The influence of the Internet and a highly dynamic telecommunications market has raised demands for increased flexibility in communication systems while controlling costs. These influences necessitate a significant rethinking of the next generation network architecture. The main themes for the new networking mindset are convergence, consolidation, migration and simplification.
The service layer of the next generation network will in all likelihood, consist of a multi service capable IP network. The ubiquity, simplicity and openness of IP make it a natural catalyst for new applications, services, traffic and, consequently, new revenues. Developments in industry standards for IP quality of service and multi protocol label switching (MPLS) based traffic engineering provide the required technical capabilities to enable a multi service IP network.
Increasingly, IP-MPLS technology development is validating the qualities of ATM by emulating many of its features and functions to such an extent that a convergence of IP-MPLS and ATM in the core is a reality. One of the earliest examples of this convergence is the introduction of ATM mediation over an IP-MPLS core where ATM traffic can be transparently tunneled through an IP-MPLS backbone using LSPs. Such a converged network core accommodates all types of traffic new and old and is well positioned to provide significant cost saving options for network operators looking to consolidate core networks.
Many traditional services, such as leased line, frame relay or cell relay are transported today over ATM networks. ATM is also the underlying technology for new digital subscriber line (DSL) and wireless local multi point distribution systems (LMDS) access applications. Just as ATM has been used to mediate a multi service traffic flow for a wide area network, there is now an opportunity to use MPLS to mediate ATM traffic across an IP-MPLS core. Mediating ATM traffic in this way enables ATM to continue to be employed at the edge of the network to adapt transport and aggregate multi service traffic.
ATM/MPLS mediating defines two encapsulation modes: cell encapsulation and packet encapsulation. Cell encapsulation allows full transparency by carrying all connection types (VCC and VPC), all AAL types and all cell types (user, OAM, RM). The packet encapsulation mode is intended mainly for AAL5 VCCs.
Today, OAM packets/cells are interpreted based on a predefined configuration comprising a fixed set of bits. The OAM packet/cell configuration is defined by standard bodies and the position and meaning of the bits cannot be changed without the necessary processes to introduce a new standard. In addition to the bit configuration the current standard specifies a number of bits that are reserved for future use. Thus, the current OAM packets/cell is statically defined in terms of location and meaning.